Upstream fixed this by commit c661c374e8df43365738daa09f4390d61bc57f08.
That's a better fix, because it doesn't change API (priority of flushes).
More info in bug 1417355 and bug 844791.
+++ This bug was initially created as a clone of Bug #1417355 +++
Fixed in Fedora 26+ via 1417355 (no regression noted so far); but as
there's no customer request for this fix, I'm closing for now. Feel free
to reopen/raise a priority.